资源描述
Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,CHAPTER 20 GLENCOE PHYSICS,Static Electricity,CHAPTER 20 GLENCOE PHYSICSStat,A.Charge,1.Charge-basis for electricity,a.two types-“+”or“-”based on the excess or deficiency of electrons.Named by Ben Franklin,b.can be created chemically,mech.,etc,c.like repel,unlike attract,A.Charge1.Charge-basis for,2.Microscopic view of Charge,a.Atom is neutral-electrons balanced by protons.Electrons in orbit around nucleus,b.With addition of energy,electrons removed leaving a positive ion.Freed electrons become attached to other material and have a negative ion.,(1)neutral objects charged by rubbing,(2)conservation of charge is critical,2.Microscopic view of Chargea,3.Conductors and Insulators,a.Insulators-materials through which charges do not move easily.Charges removed from one area are not replaced by charges from another area,b.Conductors-materials such as metals that allow charges to move,(1)Charge is carried by the movement of electrons.,3.Conductors and Insulatorsa.,(2)metals have an electron that can be easily removed as electrons act as though they belong to the entire whole-an electron cloud,(3)Air is an insulator,but under certain conditions sparks can occur.,(2)metals have an electron th,4.Concentration of Charge,a.charged body distributes charge over the surface,b.distributed to bring about equilibrium,c.pointed surfaces have a higher concentration of charge,d.Grounding-same charge per unit area,removal of excess charge.,4.Concentration of Chargea.c,B.Electric Force,1.more powerful than gravity and both attractive and repulsive,2.Charging by Conduction-charging a neutral body by touching it with a charged body.Positive or negative,3.Charged by induction-charge an object without touching,B.Electric Force 1.more powe,3.Coulombs Law,a.1785-Charles Coulomb devises an experiment to measure the electric force.,b.“The magnitude of the force that a tiny sphere with charge,q,exerts on a second sphere with charge,q,separated by a distance d,is given by the equation,3.Coulombs Lawa.1785-Char,(1)Force that q exerts on q and that q exerts on q,(2)What concept is this analogous to?,c.Hold for point charges or spherically shaped charges.Distance is between the centers of such objects.,(1)Force that q exerts on q,d.Unit of charge is the Coulomb(C),(1)one coulomb is the charge on 6.25 x 10,18,electrons,(2)lightning bolt is about 7-10 C,(3)elementary charge is the charge on one electron-negative 1.60 x 10,-19,C,e.For charge in Coulombs,distance in meters,and force in Newtons k=9 x 10,9,N-m,2,/C,2,d.Unit of charge is the Coulo,f.Electric Force-a vector quantity,must show direction.,(1)repulsive forces-positive signs,force on object is away from second object.,(2)attractive forces-negative signs,force on object is toward second object.,g.A charged object is always attracted by a neutral object(and,by 3rd Law,a neutral object is attracted to a charged object),f.Electric Force-a vector q,4.Problems,a.Two point charges of magnitude 3 x 10,-9,C and 6 x 10,-9,C are separated by 30 cm.Find the force of repulsion.F=(9x10,9,)(3x10,-9,)(6x10,-9,)/.3,2,=1.8 x10,-6,N,4.Problemsa.Two point charg,b.A 4.5 x 10,-9,C charge is located at 3.2 m from a-2.8 x 10,-9,C charge.Find the electrostatic force.,c.An electron and a proton of a hydrogen atom are separated by a distance of 5.3 x 10-11 m.An electron has a charge of-1.60 x 10-19 C and a mass of 9.11 x 10-31 kg.A proton has a mass of 1.67 x 10-27 kg.Find the electrostatic and gravitational forces between the two.How could you find the speed of the electron?Find it.,b.A 4.5 x 10-9 C charge is l,a.F=-1.11 x 10,-8,N Attractive,b.F,G,=3.6 x 10,-47,N attractiveF,E,=-8.2 x 10,-8,N attractiveFc=F,G,+F,E,=m v,2,/rtherefore v=2.18 x 10,6,m/s,a.,5.Principle of Superposition,a.When two or more charges affect a different charge,the resultant force acting on the charge equals the vector sum of the various individual charges present.,b.A 2.2 x 10,-9,C charge is located at x=-1.5m,a 5.4 x 10,-9,C is located at x=2 m,and a 3.5 x 10,-9,C charge is located at the origin.Find the net force acting on the charge at the origin.,5.Principle of Superpositiona,F,3-2,=3.08 x 10,-8,NF,3-1,=4.25 x 10,-8,N F,net,=F,3-1,-F,3-2,=1.17 x 10,-8,N towards q,2,+,+,+,q,1,1.5 q,3,2 m q,2,F,3-2,F,3-1,F 3-2=3.08 x 10-8 N,c.For extra credit.Determine the resultant force acting on charge q,3,in the following situation.q,1,=6 x 10,-9,C q,2,=-2 x 10,-9,C 4m q,3,=5 x 10,-9,C 3 m,q,2,q,3,q,1,c.For extra credit.Determin,
展开阅读全文